Pharmacology of procaine in the horse: evidence against the existence of a “procaine – penicillin” complex.

The research paper shows a study carried out to verify the existence of a “procaine-penicillin” complex in horses. The results showed no evidence of such a complex, disputing a previous theory that suggested it existed in both in vitro and in vivo situations.

Objective of the Study

The main objective of the study was to test the theory that a so-called “procaine-penicillin” complex exists in vitro and in vivo within horses. The supposed complex, because it is not dissociated into ions, was believed to be resistant to hydrolysis by plasma esterases in the horse’s body as well as unresponsive to pharmacologic receptors for procaine.

• The researchers sought to establish whether this complex was an actual physiological occurrence or just a theoretical concept.
• They delineated their experiments to demonstrate the dissociation or not of procaine and penicillin when administered in a combined form in the horses.

Methodology

Various experiments were conducted to verify the existence, or the lack thereof, of this procaine-penicillin complex.

• Procaine penicillin was administered to horses intramuscularly, with subsequent measurements taken of the procaine levels in the horse’s blood. This was compared to procaine or procaine penicillin added to equine blood in a laboratory setting.
• In an in-vitro setup, procaine and procaine penicillin were analyzed for any difference in their rate of split by blood or plasma esterases.
• The partitioning of procaine from procaine penicillin into benzene was studied over a time period to determine the lifelong existence of this supposed complex.
• Thin layer chromatography in two dimensions was also performed as another means to validate the theory.

Results

The study outcomes did not provide any supporting evidence for the existence of a procaine-penicillin complex.

• Results showed that about 90% of the procaine in the horse’s blood did split at the same rate as procaine or procaine penicillin added to equine blood in a laboratory setting.
• Similarly, procaine and procaine penicillin, in both physical and physiological conditions, displayed similar characteristics, including their rate of split by blood or plasma esterases and their partitioning into various organic solvents.
• There was no evidence found to support the formation of this complex under the experiment conditions, neither in the blood samples nor during the thin layer chromatography process.
• The findings of all the experiments disputed the theory and implications of the existence of a procaine-penicillin complex.

Conclusion

The results of the study revealed no evidence supporting the existence of a procaine-penicillin complex, both under physical and physiological conditions. Consequently, the research refutes the pharmacologic and forensic implications of the “procaine-penicillin” hypothesis.